Urea,(NH2)2CO, is a colorless organic chemical compound also known by the International Nonproprietary Name (rINN) carbamide, as established by the World Health Organization. It is highly soluble in water and has a pKa close to zero. Urea is essentially the waste produced when the body metabolizes protein. It is not only produced by humans, but also by many other mammals, as well as amphibians and some fish. Urea was the first natural compound to be artificially synthesized using inorganic compounds — a scientific breakthrough.
The primary raw material used to manufacture urea is natural gas, which ties the costs directly to gas prices. Consequently, new plants are only being built in areas with large natural gas reserves where prices are lower. Finished product is transported around the globe in large shipments of 30,000 metric tons. The market price for urea is directly related to the world price of natural gas and the demand for agricultural products. Prices can be very volatile, and at times, unpredictable. TCC is positioned to know the world markets and keep your prices competitive.
Over 90 percent of the world’s production of the substance is used for fertilizer-related products. When used in this way, it usually takes the form of granules, prills, or crystals. Farmers manually distribute the substance or it is scattered in the appropriate form with the aid of farming equipment. Urea is considered an effective feed, since it contains nitrogen, which can aid animal growth. The relatively cheap price of products made with the substance also makes this feed a popular choice by many farmers.
French chemist Hillaire Rouelle discovered urea in 1773. In 1828, just 55 years after its discovery, urea became the first organic compound to be synthetically formulated, this time by a German chemist named Friedrich Wöhler, one of the pioneers of organic chemistry. Wöhler obtained urea by treating silver isocyanate with ammonium chloride in a failed attempt to prepare ammonium cyanate.
Synthetic urea is created from synthetic ammonia and carbon dioxide and can be produced as a liquid or a solid. The process of dehydrating ammonium carbamate under conditions of high heat and pressure to produce urea was first implemented in 1870 and is still in use today. Uses of synthetic urea are numerous and therefore production is high. Approximately one million pounds of urea is manufactured in the United States alone each year, most of it used in fertilizers. Nitrogen in urea makes it water soluble, a highly desired property in this application.
Urea was found to be useful for commercial and industrial applications in the production of some types of plastics, animal feed, glues, toilet bowl cleaners, dish washing machine detergents, hair coloring products, pesticides, and fungicides. Medicinally, it is incorporated in the manufacture of barbiturates, dermatological products that re-hydrate the skin, and diuretics.
Urea is naturally produced when the liver breaks down protein or amino acids, and ammonia. The kidneys then transfer the urea from the blood to the urine. Extra nitrogen is expelled from the body through urea, and because it is extremely soluble, it is a very efficient process. The average person excretes about 30 grams of urea a day, mostly through urine, but a small amount is also secreted in perspiration.
Physicians found that urea levels can be used to detect diseases and disorders that affect the kidneys, such as acute kidney failure or end-stage renal disease (ESRD). The blood urea nitrogen (BUN) and the urine urea nitrogen (UUN) tests, which measure urea nitrogen levels in the blood and urine, are often used to assess how well a patient’s kidneys are functioning. Increased or decreased urea levels, however, do not always indicate kidney problems, but instead may reflect dehydration or increased protein intake.
More than 90 percent of world urea production is destined for use as a nitrogen-release fertilizer. Urea has the highest nitrogen content of all solid nitrogenous fertilizers in common use (46.7%). Therefore, it has the lowest transportation costs per unit of nitrogen nutrient.
In the soil, it hydrolyses back to ammonia and carbon dioxide. The ammonia is oxidized by bacteria in the soil to nitrate, which can be absorbed by the plants. Urea is also used in many multi-component solid fertilizer formulations. Urea is highly soluble in water, therefore, very suitable for use in fertilizer solutions (in combination with ammonium nitrate: UAN), e.g., in ‘foliar feed’ fertilizers. For fertilizer use, granules are preferred because of their narrower particle size distribution, an advantage for mechanical application.
The most common impurity of synthetic urea, biuret, must be present at less than 2 percent of the time, as it impairs plant growth.
Urea is spread at rates between 40 and 300 kg/ha, but actual spreading rates will vary according to farm type and region. It is better to make several small to medium applications at intervals to minimize leaching losses and increase efficient use of the Nitrogen applied, compared with single heavy applications. During summer, urea should be spread just before, or during rain to reduce possible losses from volatilization (process wherein nitrogen is lost to the atmosphere as ammonia gas). Urea should not be mixed with other fertilizers, as problems of physical quality may result.
Because of the high nitrogen concentration in urea, achieving an even spread is important. The application equipment must be calibrated correctly and used properly. Drilling must not occur on contact with or close to seeding due to the risk of germination damage. Urea dissolves in water to be applied as a spray or through irrigation systems.
In grain and cotton crops, urea is often applied at the time of the last cultivation before planting. In high rainfall areas and on sandy soils (where nitrogen can be lost through leaching) and where good in-season rainfall is expected, urea can be side or top-dressed during the growing season. Top-dressing is also popular on pasture and forage crops. In cultivating sugarcane, orea is side-dressed after planting, and applied to each ratoon crop.
For irrigated crops, urea can be applied dry to the soil, or dissolved and applied through the irrigation water. Urea will dissolve in its own weight in water, but it becomes increasingly difficult to dissolve as the concentration increases. Dissolving urea in water is endothermic, causing the temperature of the solution to fall when urea dissolves.
When preparing urea solutions for fertigation (injection into irrigation lines), dissolve no more than 30 kg of urea per 100 L of water.
In foliar sprays, 0.5 to 2.0 percent concentrations of urea are often used for horticultural crops. As urea sprays may damage crop foliage, advice for specific amounts should be sought before use. Low-biuret grades of urea should also be used if urea sprays are to be applied regularly or to sensitive horticultural crops.
Like most nitrogen products, urea absorbs moisture from the atmosphere. Therefore it should be stored either in closed/sealed bags on pallets, or, if stored in bulk, under cover with a tarpaulin. As with most solid fertilizers, it should also be stored in a cool, dry, well-ventilated area.
Urea is a raw material used in the manufacture of many important chemicals, such as:
- Various plastics, especially the Urea-formaldehyde resins
- Various adhesives, such as Urea-formaldehyde or the urea-melamine-formaldehyde used in marine plywood
- Potassium cyanate, another industrial feedstock
- Urea nitrate, an explosive
Urea has the ability to trap many organic compounds in the form of clathrates. The organic compounds are held in channels formed by interpenetrating helices comprising of hydrogen-bonded urea molecules. This behavior can be used to separate mixtures, and has been used in the production of aviation fuel and lubricating oils, and in the separation of paraffin.
As the helices are interconnected, all helices in a crystal must have the same molecular handedness. This is determined when the crystal is nucleated and can thus be forced by seeding. The resulting crystals have been used to separate racemic mixtures.
Urea is used in SNCR and SCR reactions to reduce the NOx pollutants in exhaust gases from combustion, for example, from power plants and diesel engines. The BlueTec system, for example, injects water-based urea solution into the exhaust system. The ammonia produced by decomposition of the urea reacts with the nitrogen oxide emissions and is converted into nitrogen and water within the catalytic converter.
Other commercial uses
- A stabilizer in nitrocellulose explosive
- A component of animal feed, providing a relatively cheap source of nitrogen to promote growth
- A non-corroding alternative to rock salt for road de-icing, and the resurfacing of snowboarding half pipes and terrain parks
- A flavor-enhancing additive for cigarettes
- A main ingredient in hair removers such as Nair or Veet
- A browning agent in factory-produced pretzels
- An ingredient in some hair conditioners, facial cleansers, bath oils, skin softeners, and lotions
- A reactant in some ready-to-use cold compresses for first-aid use, due to the endothermic reaction it creates when mixed with water
- A cloud seeding agent, along with other salts
- A flame-proofing agent, commonly used in dry chemical fire extinguisher charges such as the urea-potassium bicarbonate mixture.
- An ingredient in many tooth whitening products
- An ingredient in dish soap
- Along with ammonium phosphate, as a yeast nutrient, for fermentation of sugars into ethanol
- A nutrient used by plankton in ocean nourishment experiments for geoengineering purposes
- As an additive to extend the working temperature and open time of hide glue
- As a solubility-enhancing and moisture-retaining additive to dye baths for textile dyeing or printing
Urea in concentrations up to 10 M is a powerful protein denaturant as it disrupts the noncovalent bonds in the proteins. This property can be exploited to increase the solubility of some proteins. A mixture of urea and choline chloride is used as a deep eutectic solvent, a type of ionic liquid.
Urea can serve as a hydrogen source, for subsequent power generation in a fuel cell. Urea present in urine/wastewater can be used directly (though bacteria normally quickly degrade Urea.) Producing hydrogen by electrolysis of urea solution occurs at a lower voltage and uses less energy than by electrolysis of water.
Urea is used in topical dermatological products to promote rehydration of the skin. If covered by an occlusive dressing, 40 percent urea preparations may also be used for non-surgical debridement of nails. This drug is also used as an earwax removal aid.
Like saline, urea injection is used to perform abortions. It is also the main component of an alternative medicinal treatment referred to as urine therapy.
The blood urea nitrogen (BUN) test is a measure of the amount of nitrogen in the blood that comes from urea. It is used as a marker of renal function.
Urea labeled with carbon-14 or carbon-13 is used in the urea breath test, which is used to detect the presence of the bacteria Helicobacter pylori (H. pylori) in the stomach and duodenum of humans, associated with ulcers. The test detects the characteristic enzyme urease, produced by H. pylori, by a reaction that produces ammonia from urea. This increases the pH (reduces acidity) of the stomach environment around the bacteria. Similar bacteria species to H. pylori can be identified by the same test in animals such as apes, dogs, and cats (including big cats).
Urea is a safe, non-corrosive fertilizer alternative for de-icing. The chemical is easy to use on runways and walkways as well as on landing gears and other vital parts located on the under-carriage of aircraft that must always be protected from corrosion. Airports in many areas that can’t use highly corrosive chloride salts for de-icing operations use urea as the preferred alternative.